Network Traffic Engineering

Network Traffic Engineering


network traffic engineering


Network Traffic Engineering

In today’s interconnected world, network traffic engineering plays a crucial role in optimizing the performance and efficiency of computer networks. This blog post aims to provide a comprehensive overview of network traffic engineering, its importance, and the techniques used to manage and control traffic flow.

Network traffic engineering efficiently manages and controls the flow of data packets within a computer network. It involves analyzing network traffic patterns, predicting future demands, and implementing strategies to ensure smooth data transmission.


Highlights: Network Traffic Engineering

  • Network Flow Model

In a computer network, an important function is to carry traffic efficiently, given the routing paradigm in place. This efficiency is achieved through traffic engineering. Network flow models are used for network traffic engineering and can help determine routing decisions. Network Traffic engineering (TE) is the engineering of paths that can carry traffic flows that vary from those chosen automatically by the routing protocol(s) used in that network.

  • The Role of MPLS Networking

Therefore, we can engineer the paths that better suit our application. We can do this in several ways, such as standard IP routing, MPLS, or OpenFlow protocol. When considering network traffic engineering and MPLS OpenFlow, let’s start with the basics of traffic engineering and MPLS networking.


Related: You may find the following posts useful for pre-information:

  1. Transport SDN
  2. Network Visibility
  3. Load Balancing
  4. Chaos Engineering Kubernetes
  5. Segment Routing
  6. What is OpenFlow
  7. DMVPN Phases


MPLS OpenFlow.

Key Network Traffic Engineering  Discussion Points:

  • Introduction to network traffic engineering and what is involved.

  • Highlighting the different components of an MPLS network and how they work.

  • MPLS traffic engineering (TE).

  • Controller-based networking and its advantages.

  • Discussing a predictable Traffic Engineering solution.


Back to basics: Network traffic engineering

Traffic Engineering

Main Traffic Engineering Components

Network Traffic Engineering

  • Optimal Resource Utilization

  • Enhanced Quality of Service (QoS)

  • Scalability

  • Example: MPLS TE

Importance of Network Traffic Engineering

Efficient network traffic engineering is essential for several reasons:

1. Optimal Resource Utilization: By balancing network resources, traffic engineering helps minimize congestion and maximize bandwidth utilization, improving network performance.

2. Enhanced Quality of Service (QoS): Traffic engineering techniques prioritize critical applications, ensuring they receive the necessary bandwidth and reduce latency, improving user experience and customer satisfaction.

3. Scalability: With proper traffic engineering, networks can accommodate increased traffic demands, scalability, and future growth without significant performance degradation.

Techniques Used in Network Traffic Engineering

Here are some commonly used techniques in network traffic engineering:

1. Traffic Monitoring and Analysis: Network administrators employ tools to monitor and analyze traffic patterns, helping them identify bottlenecks, congestion points, and potential network vulnerabilities.

2. Traffic Shaping: Traffic shaping involves regulating network traffic flow to optimize performance. It can prioritize certain types of traffic, delay less critical traffic, and prevent data bursts that may overload network resources.

3. Load Balancing: Load balancing distributes network traffic across multiple paths or devices, preventing congestion and ensuring efficient use of available resources.

4. Quality of Service (QoS): QoS mechanisms prioritize specific types of traffic, ensuring that critical applications receive the necessary resources and reduce latency.

5. Traffic Engineering Protocols: Network engineers utilize RSVP (Resource Reservation Protocol) and MPLS (Multiprotocol Label Switching) to manage network traffic and allocate resources effectively and dynamically.

Lab on MPLS Forwarding

In the following guide, we have an MPLS network. MPLS networks have devices with different roles. So, we have the core node called the “P” provider and the “PE” provider edge nodes. The beauty of MPLS forwarding is that we can have scale in the network’s core. The P nodes do not need customer routes from the CE devices. These are usually carried out in BGP.


However, with an MPLS network, we have MPLS forwarding between the loopbacks. Notice the diagram below. The loopback address of and belong to the PE nodes. The P node is entirely unaware of any BGP routing.

MPLS overlay
Diagram: MPLS Overlay


Traffic Engineering: Inbound and Outbound

Before you can understand how to use MPLS to do traffic engineering, you must understand what traffic engineering is. So, we have network engineering that manipulates your network to suit your traffic. You make the most reasonable predictions about how traffic will flow across your network and then order the right components.

Then we have traffic engineering. Network traffic engineering is manipulating your traffic to fit your network. Traffic engineering is not MPLS-specific and is a general practice among all networking and security technologies. Traffic engineering could be a simple or complex implementation. Something as simple as tweaking IP metrics on the interface can be implemented in its simplest for traffic engineering. Then, we have traffic engineering specific to MPLS.

Network traffic engineering
Diagram: Network Traffic Engineering. Source AWS


Lab on MPLS TE

In this lab, we will look at MPLS TE with ISIS configuration. Routers PE1, P1, P2, P3, and PE2 are our MPLS core network. The CE1 and CE2 routers use regular IP routing. All routers are configured to use IS-IS L2. 

Tip: There are four main items we have to configure:

  • Enable MPLS TE support:
    • Globally
    • Interfaces
  • Configure IS-IS to support MPLS TE.
  • Configure RSVP.
  • Configure a tunnel interface.
Diagram: MPLS TE


Understanding MPLS and MPLS forwarding

MPLS is the de facto technology for service provider WAN networks. Its scalable architecture moves complexity and decision-making to the network’s edges, leaving the core to label switch packets efficiently. The PE nodes sit at the edge and perform path calculations and encapsulations. The P nodes sit in the core and label switch packets. They only perform MPLS switching and have no visibility of customer routes.

Edge MPLS routers map incoming packets into forwarding equivalence classes (FEC) and use a different label-switched path (LSP) for each forwarding class. Keeping the network core simple enables scalable network designs. Many of today’s control planes encompass a distributed architecture and can make forwarding decisions independently.

MPLS control plane still needs a distributed IGP (OSPF and ISIS) to run in the core and a distributed label allocation protocol (LDP) to label packets. Still, it shifted how we think of control planes and distributed architectures. MPLS reduced the challenges of some early control plane approaches but proposes challenges by not having central visibility, especially for traffic engineering (TE).

MPLS forwarding
Diagram: MPLS Forwarding. The source is NetworkInterview.


  • Example Technology: DMVPN Phase 3 Traffic Manipulation

DMVPN Phase 3 is the third and final phase of a Dynamic Multipoint Virtual Private Network DMVPN setup. This phase is focused on implementing the DMVPN tunnel and enabling dynamic routing. The tunnel is built between multiple network points, allowing communication between them.

In DMVPN Phase 1, the spoke devices rely on the configured tunnel destination to identify where to send the encapsulated packets. Phase 3 DMVPN uses mGRE tunnels and depends on NHRP redirect and resolution request messages to determine the NBMA addresses for destination networks.

Packets flow through the hub in a traditional hub-and-spoke manner until the spoke-to-spoke tunnel has been established in both directions. Then, as packets flow across the hub, the hub engages NHRP redirection to find a more optimal path with spoke-to-spoke tunnels.


NHRP Routing Table Manipulation

NHRP tightly interacts with the routing/forwarding tables and installs or modifies routes in the Routing Information Base (RIB), also known as the routing table, as necessary. If an entry exists with an exact match for the network and prefix length, NHRP overrides the existing next hop with a shortcut. The original protocol is still responsible for the prefix, but the percent sign (%) indicates overwritten next-hop addresses in the routing table.

DMVPN Phase 3
Diagram: DMVPN Phase 3 configuration


Lab Guide on DMVPN Phase 3

The following example shows DMVPN Phase 3 running on the network.

DMVPN Phase 3 is the latest iteration of the DMVPN technology, offering enhanced scalability and flexibility compared to its predecessors. It builds upon the foundation of Phase 1 and Phase 2, incorporating improvements that address the limitations of these earlier versions.

One of the critical features of DMVPN Phase 3 is the addition of a hub-and-spoke network topology. This allows for a centralized hub connecting multiple remote spokes, creating a dynamic and efficient network infrastructure. The hub is a central point for all spokes, enabling secure communication. In our case below, R11 is the hub, and R31 and R41 are the spokes.


Once the hub site receives traffic indicating spoke to spoke traffic, it sends back a “Traffic Indication” message. Notice the output from the debug command below. Via NHRP, the spoke knows a better path to reach the other spoke, not via the hub. The spoke then proceeds to build spoke-to-spoke tunnels.

DMVPN Phase 3
Diagram: DMVPN Phase 3 configuration


Network Traffic Engineering and MPLS 

MPLS was very successful, and significant service provider networks could support many customers by employing MPLS-style architecture. End-to-end Label Switch Paths (LSP) are extended to interconnect multiple MPLS service providers, route reflectors, and BGP confederations for large-scale deployments and complexity reduction.

However, no matter how scalable the MPLS architecture could be, you can’t escape the fact that Inter-DC circuit upgrades are time-consuming and expensive. To help alleviate this, MPLS providers introduced MPLS Traffic engineering (TE). TE moves traffic to other parts of the network to underutilized sections.

While simple TE can be done with IGP metrics, they don’t satisfy unique traffic class requirements. Therefore, provider networks commonly deploy MPLS RSVP/ TE. This type of TE enhances IGP metric tuning, allowing engineers to forward core traffic over non-shortest paths. The non-shorted path is used to avoid network “hot spots.” Since the traffic is now moved to other underutilized network parts, it prevents the lengthy process of upgrading congested core links. MPLS TE distributes traffic optimally across a network. “MPLS RSVP/ TE is a widely adopted and well-defined technology. Can SDN and OpenFlow do a better job?”


Network Traffic Engineering
Diagram: Network traffic engineering.


Holistic visibility – Controller-based networking

MPLS/TE is a distributed architecture. There is no real-time global view of the end-to-end network path. The lack of a global view may induce incorrect traffic engineering decisions, lack of predictability, and deterministic scheduling of LSPs.

Some tools work with MPLS TE to create a holistic view, but they are usually expensive and do not offer a “real-time” picture. They often make an offline topology. They also don’t change the fact that MPLS is a distributed architecture.

The significant advantage of a centralized SDN and OpenFlow framework, commonly called MPLS OpenFlow, is that you have a holistic view of the network, controller-based networking. The centralized software sits on the controllers, analyzing and controlling the production network forwarding paths. It has a real-time network view and gains insights into various network analytics about link congestion, delay, latency, drops, and other performance metrics.


mpls openflow
Diagram: MPLS OpenFlow


MPLS OpenFlow can push down rules to the nodes per-flow basis, offering a granular approach to TE. Per-flow TE state is challenging to achieve with the traditional TE mechanism. OpenFlow’s finer granularity is also evident in service insertion use casesIn addition, OpenFlow 1.4 supports better statistics that give you visibility into application performance.

This metric and a central viewpoint can only enhance traffic engineering decisions. Let’s face it: MPLS RSVP/TE, while widely deployed, involves several control plane protocols. All these protocols need to interact and work together.

The OpenFlow MPLS protocol steers traffic over MPLS using OpenFlow.

You can direct traffic from OpenFlow networks over MPLS LSP tunnel cross-connects and logical tunnel interfaces over MPLS networks. By stitching OpenFlow interfaces to MPLS label-switched paths (LSPs), you can direct OpenFlow traffic onto MPLS networks. In addition, through MPLS LSP tunnel cross-connects between interfaces and LSPs, you can connect the OpenFlow network to a remote network by creating MPLS tunnels that use LSPs as conduits.

MPLS OpenFlow
Diagram: MPLS OpenFlow. The source is Juniper.


Network state vs. Centralized end-to-end visibility

RSVP requires that some state is stored on the Label Switch Router (LSR). The state is always bad for a network and imposes control plane scalability concerns. The network state is also a target for attack. Hierarchical RSVP was established to combat the state problem, but in my opinion, it adds to network complexity. All these kludges become an operational nightmare and require skilled staff to design, implement, and troubleshoot.

Removing MPLS signaling protocols from the network and the state they need to maintain eliminates some of the scale concerns with MPLS TE. Distributed control planes must maintain many tables and neighbor relationships (LSDB and TED). They all add to network complexity.

Predictable and deterministic TE solution

Using SDN and OpenFlow for traffic engineering provides a more predictable and deterministic TE solution. Informing the OpenFlow controller that you want the traffic redirected toward a specific MAC address, the necessary forwarding entries are programmed and automatically appear across the path. There are possibilities with NETCONF and MPLS-TP, but they operationally cause problems and don’t alleviate the distributed signaling protocols.

Having a central controller view, the contents of the network allow for particular network touchpoints. New features are implemented in the software and pushed down to the individual nodes. Similar to all SDN architectures, fewer network touchpoints increase network agility. The box-by-box and manual culture is slowly disappearing.

Challenges and Future Trends

Network traffic engineering faces several challenges, including ever-increasing data volumes, evolving network architectures, and the rise of new technologies such as cloud computing and the Internet of Things (IoT). However, emerging trends like Software-Defined Networking (SDN) and Artificial Intelligence (AI) are promising to address these challenges and optimize network traffic.

Summary: Network Traffic Engineering

Understanding Network Traffic Engineering

Network traffic engineering analyzes and manipulates network traffic to enhance performance and meet specific objectives. It involves various techniques such as traffic shaping, route optimization, and load balancing. By intelligently managing the flow of data packets, network administrators can ensure optimal utilization of available bandwidth and minimize latency issues.

Traffic Engineering Techniques

Traffic Shaping

Traffic shaping is a technique used to control network traffic flow by enforcing predetermined bandwidth limits. It allows administrators to prioritize critical applications or services, ensuring smooth operation during peak traffic hours. By regulating the rate at which data packets are transmitted, traffic shaping helps prevent congestion and maintain a consistent user experience.

Route Optimization

Route optimization focuses on selecting the most efficient paths for data packets to travel across a network. Network engineers can determine the optimal routes that minimize delays and packet loss by analyzing various factors such as latency, bandwidth availability, and network topology. This ensures faster data transmission and improved overall network performance.

Load Balancing

Load balancing is a technique that distributes network traffic across multiple paths or devices, avoiding bottlenecks and optimizing resource utilization. By evenly distributing the workload, load balancers ensure that no single component is overwhelmed with traffic, thereby improving network efficiency and preventing congestion.

Benefits of Network Traffic Engineering

Enhanced Performance

By implementing traffic engineering techniques, network administrators can significantly enhance network performance. Reduced latency, improved throughput, and minimized packet loss contribute to a smoother and more efficient network operation.

Scalability and Flexibility

Network traffic engineering enables scalability and flexibility in network design. It allows for the efficient allocation of resources and the ability to adapt to changing traffic patterns and demands. This ensures that networks can handle increasing traffic volumes without sacrificing performance or user experience.

Effective Resource Utilization

Optimized network traffic engineering ensures that network resources are utilized effectively, maximizing the return on investment. By efficiently managing bandwidth and routing paths, organizations can avoid unnecessary expenses on additional infrastructure and improve overall cost-effectiveness.

Challenges and Considerations

While network traffic engineering offers numerous benefits, it also comes with its own set of challenges. Factors such as dynamic traffic patterns, evolving network technologies, and security considerations must be considered. Network administrators must stay updated with industry trends and continuously monitor and analyze network performance to address these challenges effectively.

Conclusion: Network traffic engineering is a critical discipline that ensures computer networks’ efficient and reliable functioning. By employing various techniques and protocols, network administrators can optimize resource utilization, enhance the quality of service, and pave the way for future network scalability. As technology evolves, staying updated with emerging trends and best practices in network traffic engineering will be crucial for organizations to maintain a competitive edge in today’s digital landscape.


MPLS openflow

Matt Conran
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